What is PlayViz?
PlayViz gives you a measure of how well each team is performing in each area of the game. The output is a plus or minus score measured in runs, which tells you the impact of a team’s batting, bowling and fielding performances so far, compared to an average Test team in the same conditions.
How does it work?
In simple terms Test cricket is a game where the batting side are trying to score as many runs as they can, whilst losing as few wickets as possible. The bowlers are trying to do the opposite, take wickets whilst conceding as few runs as possible. The fielders are trying to assist the bowlers in doing so. PlayViz rates the teams on how well they have done in each of these areas, compared to how an average Test team would do under the same conditions.
For example, if a side is 90 for 3, but an average Test team would have scored 125 for the first 3 wickets, then the batting team will have a PlayViz score of -35; they are 35 runs below what they should be against this opposition in these conditions.
How do you know what an average team would score on this pitch against this opposition?
The system looks at previous matches played at this venue and in the host country and adjusts the expected scores accordingly. If it is a high scoring venue then the expected scores are adjusted upwards. If a ground has historically had scores which are 10% higher than Test average, then expected scores are increased by 10% etc.
The opposition bowling attack is also factored in. Against a weak attack expected scores will be adjusted upwards, against a strong attack they are adjusted downwards. The collective averages of the bowlers are used to determine the weighting.
How do you factor in fielding performance?
Every incident in the field that affects the score is recorded and evaluated. This includes catches, run outs, missed chances, miss-fields and run-saving stops.
PlayViz works from a system that assigns a plus or minus value in runs to each piece of fielding indicating how much it has changed the team’s total. For wickets or missed chances this is done by taking the batsman’s expected average for the innings.
As well as the value, each incident is assigned a par %. This is the expected percentage success rate for this skill in Test cricket. For example, slip catches are held 70% of the time in Test cricket, so a standard slip catch would have a par % of 70%.
The run value of the piece of fielding is then calculated using these two values.
A batsman has an expected average of 40 in this match and gives a standard slip chance (par 70%).
If the catch is held, then the PlayViz fielding score is:
+30% x 40 = +12 runs.
If the chance is dropped, then the PlayViz fielding score is:
-70% x 40 = -28 runs.
If the catch is held, the fielding has been 12 runs better than the average outcome. If it is dropped, it has been 28 runs worse than the average outcome.
A lower order batsman has an expected average of 12 in this match. He is involved in a run out chance. A typical shy at the stumps from a fielder in the ring has a 25% success rate in Tests, so
If the fielder effects the run out, the PlayViz fielding score is:
+75% x 12 = +9 runs.
If the fielder misses, the PlayViz fielding score is:
-25% x 12 = -3 runs.
A fielder makes a mistake on a regulation pick-up in the covers and the batsmen run two as a result. Here the scoring is easy; the nominal par % for any routine fielding is 100%, so the PlayViz fielding score is -2.
So each significant fielding event (significant means anything that affects the score) is recorded and assigned a PlayViz run value as outlined above. All of these values are added up over the course of the innings to give the PlayViz fielding score, the impact (in runs) that the teams’ fielding has had on the score.
How do you calculate the PlayViz batting and bowling scores?
The batting score is calculated as follows:
PlayViz Batting Score = Current Score – (Expected Score – Opposition Fielding Score).
The batting team are currently 90 for 3. The expected score with 3 wickets down (for an average Test team against this opposition at this venue) is 110. The Fielding score is currently +8
So, PlayViz Batting Score = 90 – (110 – 8) = -12 runs.
Similarly, the bowling score is calculated as follows:
PlayViz Bowling Score = (Expected Score – Fielding Score)– Current Score.
The score is currently 90 for 3. The expected score with 3 wickets down (for this batting side against an average Test attack at this venue) is 100. The Fielding score is currently +8:
So, PlayViz Bowling Value = (100 -8) – 90 = +2 runs.